The envelopes of multiple-fiber units which meet the specifications of the German Bundespost are made of a rigid plastic. Therefore, tools (knife, scissors, etc.) are required to remove the envelope, as is necessary in preparation for splicing, for example.
AT&T, USA, manufactures cables having a tube which contains up to 48 optical fibers (AT&T Marketing Communications 2122 B, August 1985). Bundles of 4 to 12 optical fibers are held together with color-coded yarn binders. The tube is filled with a filling compound. A tensionproof cable jacket is applied directly over the tube.
Such bundles of optical fibers permit high fiber-packing densities but require special attention during splicing, so that the fibers of the different bundles will not be mixed up. In the cables described above, an assignment of an individual optical fibers to a particular bundle at an end of a cable is hardly possible because during removal of the tube, the binders come open and all optical fibers gent into disorder.